Conventionally, a linear power supply that generates an output voltage Vout from an input voltage Vin by continuously controlling conduction degree of an output transistor is used for various applications. Note that linear power supplies are roughly classified into two types: one uses an N-channel (or an NPN) output transistor, and the other uses a P-channel (or a PNP) output transistor.
As an example of a conventional technique related to the above, there is Patent Document 1.